Brake assembly with disks of variable thickness and methods for disk reuse

ABSTRACT

A method of making a brake assembly using recycled friction disks may comprise removing a first friction disk from a worn brake assembly, removing a portion of the first friction disk to reduce a thickness of the first friction disk, and incorporating a previously unused friction disk and the first friction disk into a brake assembly comprising unworn rotor disks made of a first material. The previously unused friction disk and the first friction disk may comprise a second material different from the first material. The thickness of the first friction disk may be different from a thickness of the previously unused friction disk.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of, and claims priority to, U.S. Ser.No. 15/822,353 filed Nov. 27, 2017 and entitled “BRAKE ASSEMBLY WITHDISKS OF VARIABLE THICKNESS AND METHODS FOR DISK REUSE,” which is herebyincorporated by reference in its entirety for all purposes.

FIELD

The present disclosure relates to aircraft braking systems, and, moreparticularly, to methods for reusing friction disks in brake assemblieshaving friction disks of varying thickness.

BACKGROUND

Aircraft brake systems typically employ a brake stack comprised of aseries of friction disks, which may be forced into contact with oneanother to stop the aircraft. Hybrid brake stacks may comprise ceramicmatrix composite (CMC) friction disks alternating with carbonfiber-reinforced/carbon matrix (C/C) composite friction disks.Generally, when a hybrid brake stack reaches its wear limit (i.e., hasworn beyond a useable limit), the C/C composite disks may account forapproximately 90-95% of the total wear, while the CMC disks tend toaccount for only 5-10% of the total wear. In this regard, when the brakestack has worn beyond the usable limit, the C/C composite disks may beconsumed, with the CMC disks exhibiting very little wear; however, bothdisks are generally discarded.

SUMMARY

A brake assembly in an unworn state is disclosed herein. The brakeassembly may comprise a friction disk stack comprising a plurality ofrotors each comprising a first material, and a plurality of statorsinterleaved between the rotors. The stators may comprise a secondmaterial different from the first material. A wear rate of the firstmaterial may be different from a wear rate of the second material. Athickness of a first stator of the plurality of stators may be greaterthan a thickness of a second stator of the plurality of stators. Apressure plate may be located at a first end of the friction disk stack.The pressure plate may comprise the second material. A thickness of thepressure plate may be less than the thickness of the second stator.

In various embodiments, an end plate comprising the second material maybe located at a second end of the friction disk stack opposite the firstend of the friction disk stack. A thickness of the end plate may be lessthan the thickness of the second stator. The thickness of the end platemay be less than the thickness of the pressure plate.

In various embodiments, the first material may comprise a carbonfiber-reinforced/carbon matrix composite material. The second materialmay comprise a ceramic matrix composite material.

In various embodiments, at least one stator of the plurality of statorscomprises a recycled stator. In various embodiments, a thickness of athird stator of the plurality of stators is less than the thickness ofthe first stator and greater than the thickness of the second stator.

A method of reusing a friction disk over multiple wear cycles is alsodisclosed herein. The method may comprise forming a first brake assemblyby locating a first stator between a first rotor of the first brakeassembly and a second rotor of the first brake assembly, and locating asecond stator having a thickness different from a thickness of the firststator between the second rotor of the first brake assembly and a thirdrotor of the first brake assembly. The first stator and the secondstator may comprise a first material and the first rotor of the firstbrake assembly and the second rotor of the first brake assembly maycomprise a second material different from the first material. The firststator may comprise a first previously unused stator. The method mayfurther comprise removing the first stator and the second stator fromthe first brake assembly, and forming a second brake assembly bylocating a third stator between a first rotor of the second brakeassembly and a second rotor of the second brake assembly, andincorporating at least one of the first stator or the second stator intothe second brake assembly. The third stator may comprise a secondpreviously unused stator.

In various embodiments, the method may further comprise removing a firstportion of at least one of the first stator or the second stator priorto forming the second brake assembly.

In various embodiments, the method may further comprise removing the atleast one of the first stator or the second stator from the second brakeassembly, and forming a third brake assembly by locating a fourth statorbetween a first rotor of the third brake assembly and a second rotor ofthe third brake assembly and incorporating the at least one of the firststator or the second stator into the third brake assembly. The fourthstator may comprise a third previously unused stator.

In various embodiments, incorporating the at least one of the firststator or the second stator into the third brake assembly may compriselocating the at least one of the first stator or the second statorbetween the second rotor of the third brake assembly and a third rotorof the third brake assembly.

In various embodiments, incorporating the at least one of the firststator or the second stator into the third brake assembly may compriseusing the at least one of the first stator or the second stator as atleast one of a pressure plate of the third brake assembly or an endplate of the third brake assembly.

In various embodiments, the method may further comprise removing asecond portion of at least one of the first stator or the second statorafter the removing the at least one of the first stator or the secondstator from the second brake assembly and prior to forming the thirdbrake assembly.

In various embodiments, the first material may comprise a ceramic matrixcomposite material. The second material may comprise a carbonfiber-reinforced/carbon matrix composite material.

A method of making a brake assembly using recycled friction disks isalso disclosed herein. The method may comprise removing a first frictiondisk from a worn brake assembly. The first friction disk may comprise afirst material. The worn brake assembly may comprise a second frictiondisk comprising a second material different from the first material. Themethod may further comprise removing a portion of the first frictiondisk to reduce a thickness of the first friction disk, and incorporatinga previously unused friction disk, a third friction disk, and the firstfriction disk into an unworn brake assembly. The previously unusedfriction disk and the third friction disk may comprise the firstmaterial. The thickness of the first friction disk may be different froma thickness of the previously unused friction disk and from a thicknessof the third friction disk.

In various embodiments, the first friction disk, the previously unusedfriction disk, and the third friction disk may comprise non-rotatingcomponents of the unworn brake assembly.

In various embodiments, the first material may comprise a ceramic matrixcomposite material, and the second material may comprise a carbonfiber-reinforced/carbon material composite material.

In various embodiments, incorporating the first friction disk into theunworn brake assembly may comprise using the first friction disk as atleast one of a pressure plate or an end plate of the unworn brakeassembly.

The foregoing features and elements may be combined in variouscombinations without exclusivity, unless expressly indicated hereinotherwise. These features and elements as well as the operation of thedisclosed embodiments will become more apparent in light of thefollowing description and accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

The subject matter of the present disclosure is particularly pointed outand distinctly claimed in the concluding portion of the specification. Amore complete understanding of the present disclosures, however, maybest be obtained by referring to the detailed description and claimswhen considered in connection with the drawing figures, wherein likenumerals denote like elements.

FIG. 1 illustrates a multi-disk brake assembly comprising stator disksof varying thickness, in accordance with various embodiments;

FIG. 2A illustrates a multi-disk brake assembly comprising stator disksof varying thickness in an un-worn state, in accordance with variousembodiments;

FIG. 2B illustrates a multi-disk brake assembly in a worn state, inaccordance with various embodiments;

FIG. 2C illustrates an unworn multi-disk brake assembly comprisingrecycled stator disks of varying thickness, in accordance with variousembodiments;

FIG. 2D illustrates an unworn multi-disk brake assembly comprisingrecycled stator disks of varying thickness, in accordance with variousembodiments;

FIGS. 3A and 3B illustrate a method of reusing a friction disk overmultiple brake assembly wear cycles; and

FIG. 4 illustrates a method of making a brake assembly using recycledfriction disks, in accordance with various embodiments.

DETAILED DESCRIPTION

The detailed description of exemplary embodiments herein makes referenceto the accompanying drawings, which show exemplary embodiments by way ofillustration. While these exemplary embodiments are described insufficient detail to enable those skilled in the art to practice thedisclosure, it should be understood that other embodiments may berealized and that logical changes and adaptations in design andconstruction may be made in accordance with this disclosure and theteachings herein without departing from the spirit and scope of thedisclosure. Thus, the detailed description herein is presented forpurposes of illustration only and not of limitation.

Furthermore, any reference to singular includes plural embodiments, andany reference to more than one component or step may include a singularembodiment or step. Also, any reference to attached, fixed, connected,or the like may include permanent, removable, temporary, partial, full,and/or any other possible attachment option. Additionally, any referenceto without contact (or similar phrases) may also include reduced contactor minimal contact.

Throughout the present disclosure, like reference numbers denote likeelements. Accordingly, elements with like element numbering may be shownin the figures, but may not necessarily be repeated herein for the sakeof clarity. Cross hatching lines may be used throughout the figures todenote different parts, but not necessarily to denote the same ordifferent materials.

As used herein, “proximate” refers to a direction inward, or generally,towards the reference component. As used herein, “distal” refers to thedirection outward, or generally, away from a reference component.

Brake assemblies of the present disclosure may include brake stackscomprised of non-rotating friction disks (stator disks) splined to anon-rotating wheel axle interspersed with rotating friction disks (rotordisks) splined to the rotating wheel. In various embodiments, the brakestacks may be hybrid brake stacks including rotor disks comprised of aC/C composite material and stator disks comprised of a CMC material. Invarious embodiments, the stator disks may be of varying thickness. Forexample, the stator disk proximate the piston housing (also referred toherein as the S1 position) may be thicker than the other stator disks inan unworn state. The varying thickness of the stator disks may allow thestator disks to be reused/recycled (i.e., incorporated into a brakeassembly comprised of new/unworn rotor disks). For example, at overhaul,the stator disk located at the S1 position may be machined to clean thewear surface and then incorporated into the stator two (S2) position.Similarly, the stator disk in the S2 position may be machined and thenincorporated into a new stator position at overhaul. The variablethickness and reuse of the CMC disks tends to reduce the amount ofdiscarded material at overhaul and may also reduce the cost ofoverhauling a hybrid brake stack, as new/overhauled hybrid brake stacksmay be formed using new rotors and one new CMC stator, as opposed tousing new rotors and multiple new CMC stators.

With reference to FIG. 1, a multi-disk brake assembly 20 is illustrated,in accordance with various embodiments. Brake assembly 20 may include awheel 10 supported for rotation around axle 12 by bearings 14. Wheel 10includes rims 16 for supporting a tire, and a series of axiallyextending rotor splines 18 (one shown). Rotation of wheel 10 ismodulated by brake assembly 20. Brake assembly 20 includes pistonhousing 22, torque tube 24, a plurality of pistons 26 (one shown),pressure plate 30, and end plate 32. Torque tube 24 may be an elongatedannular structure that includes a reaction plate 34 (also referred to asa back leg) and a series of axially extending stator splines 36 (oneshown). Reaction plate 34 and stator splines 36 may be integral withtorque tube 24, as shown in FIG. 1, or they may each be attached asseparate components.

Brake assembly 20 also includes a plurality of friction disks 38. Theplurality of friction disks 38 includes at least one non-rotatablefriction disk (stator) 40, and at least one rotatable friction disk(rotor) 42. Each of the friction disks 38 includes an attachmentstructure. In various embodiments, each of the three stators 40 includesa plurality of stator lugs 44 at circumferentially spaced positionsaround stators 40 as an attachment structure. Similarly, each of thefour rotatable rotors 42 includes a plurality of rotor lugs 46 atcircumferentially spaced positions around rotor 42.

Piston housing 22 is mounted to axle 12. Torque tube 24 is bolted orotherwise coupled to piston housing 22 with reaction plate 34 of torquetube 24 proximate an axial center of wheel 10. End plate 32 is connectedto, or is otherwise frictionally engaged with, a surface of reactionplate 34 that is facing axially away from the axial center of wheel 10.End plate 32 is non-rotatable by virtue of its connection to orfrictional engagement with torque tube 24. Stator splines 36 may supportpressure plate 30 such that pressure plate 30 is also non-rotatable.Stator splines 36 may also support non-rotatable stators 40. Stators 40may engage stator splines 36 with gaps formed between stator lugs 44.Similarly, rotors 42 may engage rotor splines 18 with gaps formedbetween rotor lugs 46. Rotors 42 may be rotatable by virtue of theirengagement with rotor splines 18 of wheel 10.

In various embodiments, rotors 42 are arranged with end plate 32 on oneend, pressure plate 30 on the other end, and stators 40 interleaved suchthat rotors 42 are adjacent to non-rotatable friction components.Pistons 26 are connected to piston housing 22 at circumferentiallyspaced positions around piston housing 22. Pistons 26 face axiallytoward wheel 10 and contact a side of pressure plate 30 opposite rotors42. Pistons 26 may be powered electrically, hydraulically, orpneumatically. In response to actuation of pistons 26, a force towardsreaction plate 34 is exerted on friction disks 38 such that rotors 42and stators 40 are pressed together between pressure plate 30 and endplate 32.

In various embodiments, the non-rotating frictional components of brakeassembly 20 (i.e., pressure plate 30, end plate 32, and stators 40) maycomprise a material that is different from the material of the rotatingfrictional component (e.g., rotors 42). For example, in variousembodiments, rotors 42 comprise a C/C composite material and pressureplate 30, end plate 32, and/or stators 40 comprise CMC material. Thematerial of the rotational components may have a wear rate that differsfrom the material of the non-rotational components. Stated differently,the difference in material of the rotational and non-rotationalcomponents may cause the rotational components to wear at a rate that isdifferent from the non-rotational components. For example, therotational components may wear faster than the non-rotationalcomponents.

FIG. 2A illustrates brake assembly 20 in an unworn state. In variousembodiments, each of the rotors 42 may comprise a C/C composite disk142. In the unworn or “new” state, as illustrated in FIG. 2A, each ofthe C/C composite disks 142 comprises a thickness T1. In variousembodiments, in the unworn state, the C/C composite disks 142 areapproximately equal in thickness. As used herein, “approximately equal”means ±0.01 inches (±0.025 cm).

FIG. 2B illustrates brake assembly 20 after a wear cycle and in a fullyworn state (i.e., worn beyond a suitable operational thickness). After awear cycle of brake assembly 20, worn C/C composite disks 142 have athickness T8 that is less than thickness T1.

With continued reference to FIG. 2A, the stator 40 in the first stator(S1) position of brake assembly 20 (i.e., the stator closest to pressureplate 30) may comprise a CMC disk 130. In various embodiments, CMC disk130 may be a new or “previously unused” CMC disk. As used herein, a“previously unused” disk refers to a disk that has not been previouslyemployed in a brake assembly and/or has not been worn by virtue ofcontact with a friction disk during braking. CMC disk 130 comprisesopposing wear surfaces 230 and 231. During braking, wear surfaces 230and 231 may contact C/C composite disks 142, which may create frictionto decelerate the aircraft. In the unworn state of FIG. 2A, the CMC diskin the S1 position comprises a thickness T2. After a wear cycle of brakeassembly 20, with momentary reference to FIG. 2B, the CMC disk in S1position comprises a thickness T9 that is less than thickness T2.

The stator 40 in the second stator (S2) position of brake assembly 20(i.e., the stator that is second closest to pressure plate 30) maycomprise a CMC disk 132. In various embodiments, CMC disk 132 may be arecycled or previously used CMC disk. As used herein, a “recycled” or“previously used” disk refers to a disk that has been previouslyemployed in a brake assembly and/or has been worn by virtue of contactwith another friction disk. In various embodiments, the friction disk inthe S2 position of brake assembly 20 may be a friction disk which wasemployed as an S1 friction disk during one or more previous wearcycle(s). CMC disk 132 comprises opposing wear surfaces 232 and 233.During braking, wear surfaces 232 and 233 may contact C/C compositedisks 142, which may create friction to decelerate the aircraft. In theunworn state of FIG. 2A, the CMC disk in the S2 position comprises athickness T3. In various embodiments, thickness T3 is less thanthickness T2. In various embodiments, thickness T3 is between 85% and99% of thickness T2. In various embodiments, thickness T3 is between 88%and 97% of thickness T2. In various embodiments, thickness T3 is between90% and 95% of thickness T2. After a wear cycle of brake assembly 20,with momentary reference to FIG. 2B, the CMC disk in the S2 position hasa thickness T10 that is less than thickness T3.

The stator 40 in the third stator (S3) position of brake assembly 20(i.e., the stator that is third closest to pressure plate 30) maycomprise a CMC disk 134. In various embodiments, CMC disk 134 may be arecycled or previously used CMC disk. Stated differently, the frictiondisk in the S3 position of brake assembly 20 may be a friction diskwhich was employed as an S1 and/or an S2 friction disk during one ormore previous wear cycle(s). CMC disk 134 comprises opposing wearsurfaces 234 and 235. During braking, wear surfaces 234 and 235 maycontact C/C composite disks 142, which may create friction to deceleratethe aircraft. In the unworn state of FIG. 2A, the CMC disk in the S3position comprises a thickness T4. In various embodiments, thickness T4is less than thickness T3. In various embodiments, T4 is between 75% and89% of thickness T2. In various embodiments, thickness T4 is between 78%and 87% of thickness T2. In various embodiments, thickness T4 is between80% and 85% of thickness T2. After a wear cycle of brake assembly 20,with momentary reference to FIG. 2B, the CMC disk in the S3 position hasa thickness T11 that is less than thickness T4.

In various embodiments, pressure plate 30 may comprise a CMC disk 136.In this regard, pressure plate 30 may comprise a stator located in afourth stator (S4) position of brake assembly 20. Stated differently,the S4 position may refer to a non-rotating frictional component ofbrake assembly 20 that comprises a non-rotating friction disk having awear surface 236 oriented toward rotors 42, and a non-wear 237 surfaceoriented away from rotors 42 and toward piston 26, with momentaryreference to FIG. 1. During braking, wear surface 236 may contact a C/Ccomposite disk 142, which may create friction to decelerate theaircraft. In various embodiments, CMC disk 136 may be a recycled orpreviously used CMC disk. Stated differently, the friction disk in theS4 position of brake assembly 20 may be a friction disk which wasemployed as an S1, S2, and/or S3 friction disk during one or moreprevious wear cycle(s). In the unworn state of FIG. 2A, the CMC disk inthe S4 position comprises a thickness T5. In various embodiments,thickness T5 is less than thickness T4. In various embodiments,thickness T5 is between 65% and 79% of thickness T2. In variousembodiments, thickness T5 is between 68% and 77% of thickness T2. Invarious embodiments, thickness T5 is between 70% and 75% of thicknessT2. After a wear cycle of brake assembly 20, with momentary reference toFIG. 2B, the CMC disk in the S4 position has a thickness T12 that isless than thickness T5.

In various embodiments, end plate 32 may comprise a CMC disk 138. Inthis regard, end plate 32 may comprise a stator located in a fifthstator (S5) position of brake assembly 20. Stated differently, the S5position may be to a non-rotating frictional component of brake assembly20 that comprises a CMC disk having a wear surface 238 oriented towardrotors 42, and a non-wear 239 surface oriented away from rotors 42 andtoward reaction plate 34, with momentary reference to FIG. 1. Duringbraking, wear surface 238 may contact a C/C composite disk 142, whichmay create friction to decelerate the aircraft. In various embodiments,CMC disk 138 may be a recycled or previously used CMC disk. Stateddifferently, the friction disk in the S5 position of brake assembly 20may be a friction disk which was employed as an S1, S2, S3, and/or S4friction disk during one or more previous wear cycle(s).

In the unworn state of FIG. 2A, the CMC disk in the S5 positioncomprises a thickness T6. In various embodiments, thickness T6 is lessthan thickness T5. In various embodiments, T6 may be less than thicknessT4, but greater than or equal to thickness T5. In various embodiments,T6 is between 55% and 69% of thickness T2. In various embodiments,thickness T6 is between 58% and 67% of thickness T2. In variousembodiments, T6 is between 60% and 65% of thickness T2. After a wearcycle of brake assembly 20, with momentary reference to FIG. 2B, the CMCdisk in the S5 position comprises a thickness T13 that is less thanthickness T6.

With combined reference to FIGS. 2A and 2B, in the unworn state, brakeassembly 20 may have a thickness T7 extending from non-wear surface 237of CMC disk 136 to non-wear surface 239 of CMC disk 138. After a wearcycle, fully worn brake assembly 20 may have a thickness T14 extendingfrom non-wear surface 237 of CMC disk 136 to non-wear surface 239 of CMCdisk 138. In various embodiments, a greater portion of the differencebetween thickness T7 and thickness T14 may be caused by reduction in thethickness (or wear) of C/C composite disks 142. For example,approximately 90% of the difference between thickness T7 and thicknessT14 may be attributable to wear of C/C composite disks 142. As usedherein, “approximately” means±10%. In this regard, a relatively smallportion of CMC disks 130, 132, 134, 136, and 138 may consumed during awear cycle of brake assembly.

The wear rate of the CMC disks may allow one or more of the CMC disks tobe incorporated in unworn brake assemblies. In various embodiments, whenincorporating the CMC disks into unworn brake assemblies, the CMC disksmay be located in new stator positions, as described in further detailbelow.

FIG. 2C shows an unworn brake assembly 120 incorporating recycledfriction disks. In various embodiments, brake assembly 120 may includerecycled CMC disks 130, 132, 134, and 136 from brake assembly 20. Brakeassembly 120 may further include a previously unused CMC disk 140 in theS1 position, and a plurality of new C/C composite disks 242. A mass ofunworn brake assembly 120 may be approximately equal to the mass ofunworn brake assembly 20. As used herein “approximately equal” means ±2%of the weight of unworn brake assembly 20. For example, and as discussedin further detail below, after completing a full wear cycle, the statordisks from worn brake assembly 20 may be translated down one position inthe new brake assembly 120, and a new, previously unused disk may beintroduced in the S1 position of brake assembly 120. By introducing thepreviously unused disk, the mass of the new, unworn brake assembly isreturned to the original value (e.g., to the mass of unworn brakeassembly 20).

With combined reference to FIGS. 2B and 2C, once brake assembly 20reaches thickness T14, CMC disks 130, 132, 134, and/or 136 may beremoved from brake assembly 20 and machined (e.g., cut, ground, sanded,etc.) to clean and planarize (i.e., flatten, smooth) the wear surfacesof the CMC disks. In other words, a portion of the CMC disk may beremoved from one or both of the wear surfaces. In this regard, aftermachining the CMC disks, a thickness of CMC disk is reduced. In variousembodiments, after machining, the CMC disks are incorporated into newbrake assemblies. In various embodiments, a location of the CMC disks inthe new brake assemblies is selected based on the thickness of the CMCdisk after planarizing the wear surfaces.

In various embodiments, after a wear cycle of brake assembly 20, CMCdisk 130 may be removed from brake assembly 20 and incorporated into S2position of brake assembly 120. In various embodiments, after removingCMC disk 130 from worn brake assembly 20, wear surface 230 and 231 areplanarized. Stated differently, after removal from brake assembly 20,CMC disk 130 is thinned by removing a portion of CMC disk 130 from wearsurface 230 and wear surface 231. In various embodiments, at least 0.007inches (0.018 cm) may be removed from each of wear surface 230 and wearsurface 231, prior to incorporating CMC disk 130 into brake assembly120. In various embodiments, between 0.010 inches and 0.02 inches (i.e.,0.025 cm and 0.051 cm) of material is removed from wear surface 230 andfrom wear surface 231. The amount of material removed from wear surfaces230 and 231 may be determined based on the difference between thicknessT9 and thickness T3. For example, the amount of material removed fromwear surfaces 230 and 231 may be selected such that after removal, thethickness of CMC disk 130 equals thickness T3. In various embodiments,if after planarizing wear surfaces 230 and 231, a thickness of CMC disk130 is less than thickness T3, additional material may be removed fromsurfaces wear surfaces 230 and 231 so that CMC disk 130 can beincorporated into the S3 position of brake assembly 120 (i.e., thethickness of CMC disk 130 is reduced to thickness T4). In variousembodiments, CMC disk 130 may be employed in between 2 and 5 wearcycles. For example, CMC disk 130 may be located in the S1 positionduring a first wear cycle, in the S2 position during a second wearcycle, in the S3 position during a third wear cycle, in the S4 positionduring a fourth wear cycle, and in the S5 position during a fifth wearcycle.

With continued reference to FIGS. 2B and 2C, CMC disk 132 may be removedfrom brake assembly 20 and incorporated into the S3 position of brakeassembly 120. In various embodiments, after removing CMC disk 132 fromworn brake assembly 20, wear surfaces 232 and 233 are planarized. Stateddifferently, after removal from brake assembly 20, CMC disk 132 isthinned by removing a portion of CMC disk 132 from wear surface 232 andwear surface 233. In various embodiments, at least 0.007 inches (0.018cm) may be removed from wear surface 232 and from wear 233, prior toincorporating CMC disk 132 into brake assembly 120. In variousembodiments, between 0.010 inches and 0.02 inches (i.e., 0.025 cm and0.051 cm) of material may be removed from wear surface 232 and from wearsurface 233. The amount of material removed from wear surfaces 232 and233 may be determined based on the difference between thickness T10 andthickness T4. For example, the amount of material removed from wearsurfaces 232 and 233 may be selected such that after removal, thethickness of CMC disk 132 equals thickness T4. In various embodiments,if after planarizing wear surfaces 232 and 233, a thickness of CMC disk132 is less than thickness T4, additional material may be removed fromsurfaces wear surfaces 232 and 233 so that CMC disk 132 can beincorporated into the S4 position of brake assembly 120 (i.e., thethickness of CMC disk 132 is reduced to thickness T5).

In various embodiments, CMC disk 134 may be removed from brake assembly20 and incorporated into the S4 position of brake assembly 120. Invarious embodiments, after removing CMC disk 134 from worn brakeassembly 20, wear surfaces 234 and 235 are planarized. In variousembodiments, at least 0.007 inches (i.e., 0.018 cm) may be removed fromeach of wear surface 234 and wear surface 235. In various embodiments,between 0.010 inches and 0.02 inches (i.e., 0.025 cm and 0.051 cm) ofmaterial is removed from wear surface 234 and from wear surface 235. Theamount of material removed from wear surfaces 234 and 235 may bedetermined based on the difference between thickness T11 and thicknessT5. In various embodiments, if after planarizing wear surfaces 234 and235, a thickness of CMC disk 134 is less than thickness T5, additionalmaterial may be removed from surfaces wear surfaces 234 and 235 so thatCMC disk 134 can be incorporated into the S5 position of brake assembly120 (i.e., the thickness of CMC disk 134 is reduced to thickness T6).

In various embodiments, CMC disk 136 may be removed from brake assembly20 and incorporated into stator position S5 of brake assembly 120. Invarious embodiments, after removing CMC disk 136 from worn brakeassembly 20, wear surface 236 and/or surface 237 is/are planarized. Invarious embodiments, at least 0.007 inches (i.e., 0.018 cm) may beremoved from one or both surface 236 and/or surface 237. In variousembodiments, only one surface may be planarized as pressure plate 30 andend plate 32 each comprise one wear surface and one non-wear surface. Invarious embodiments, between 0.010 inches and 0.02 inches (i.e., 0.025cm and 0.051 cm) of material may be removed from surface 236 and/or fromsurface 237. The amount of material removed from surface 236 and/orsurface 237 may be determined based on the difference between thicknessT12 and thickness T6.

FIG. 2D shows a brake assembly 220 incorporating recycled frictiondisks. In various embodiments, brake assembly 220 may include recycledCMC disks 130, 132, 134, and 140. Brake assembly 220 may further includea previously unused CMC disk 144 in the S1 position, and a plurality ofnew C/C composite disks 342. A mass of unworn brake assembly 220 may beapproximately equal to the mass of unworn brake assemblies 20 and 120.As used herein “approximately equal” means±2% of the weight of unwornbrake assembly 20. For example, after completing a full wear cycle, eachstator disks from worn brake assembly 120 may be translated down oneposition in the new brake stack 220, and a new, previously unused diskmay be introduced in the S1 position. By introducing the new disk,previously unused the mass of the new unworn brake assembly is returnedto the original value (e.g., the mass of unworn brake assembly 20).

With combined reference to FIGS. 2C and 2D, after a wear cycle of brakeassembly 120, CMC disk 140 may be removed from brake assembly 120 andincorporated into the S2 position of brake assembly 220. In variousembodiments, after removing CMC disk 140 from worn brake assembly 120,wear surface 240 and 241 are planarized. In various embodiments, atleast 0.007 inches (0.018 cm) may be removed from wear surface 240 andfrom wear surface 241, prior to incorporating CMC disk into brakeassembly 220. In various embodiments, between 0.010 inches and 0.02inches (i.e., 0.025 cm and 0.051 cm) of material is removed from wearsurface 240 and from wear surface 241. The amount of material removedfrom wear surfaces 240 and 241 is selected such that after removal, thethickness of CMC disk 140 equals thickness T3. In various embodiments,if after planarizing wear surfaces 240 and 241, a thickness of CMC disk140 is less than thickness T3, additional material may be removed fromsurfaces wear surfaces 240 and 241 so that CMC disk 140 can beincorporated into the S3 position of brake assembly 220 (i.e., thethickness of CMC disk 140 is reduced to thickness T4).

In various embodiments, CMC disk 130 may be removed from brake assembly120 and incorporated into the S3 position of brake assembly 220. Invarious embodiments, after removing CMC disk 130 from worn brakeassembly 120, wear surfaces 230 and 231 are planarized. In variousembodiments, at least 0.007 inches (0.018 cm) may be removed from wearsurface 230 and from wear surface 231, prior to incorporating CMC disk130 into brake assembly 220. In various embodiments, between 0.010inches and 0.02 inches (i.e., 0.025 cm and 0.051 cm) of material isremoved from wear surface 230 and from wear surface 231. The amount ofmaterial removed from wear surfaces 230 and 231 is selected such thatafter removal, the thickness of CMC disk 130 equals thickness T4. Invarious embodiments, if after planarizing wear surfaces 230 and 231, athickness of CMC disk 130 is less than thickness T4, additional materialmay be removed from wear surfaces 230 and 231 so that CMC disk 130 canbe incorporated into the S4 or S5 position of brake assembly 220 (i.e.,the thickness of CMC disk 130 is reduced to thickness T5 or T6,respectively).

In various embodiments, CMC disk 132 may be removed from brake assembly120 and incorporated into stator position S4 of brake assembly 220. Invarious embodiments, after removing CMC disk 132 from worn brakeassembly 120, wear surfaces 232 and 233 are planarized. In variousembodiments, at least 0.007 inches (i.e., 0.018 cm) may be removed fromwear surfaces 232 and 233, prior to incorporating CMC disk 132 intobrake assembly 220. In various embodiments, between 0.010 inches and0.02 inches (i.e., 0.025 cm and 0.051 cm) of material is removed fromwear surface 232 and from wear surface 233. The amount of materialremoved from wear surface 232 and wear surface 233 is selected such thatafter removal, the thickness of CMC disk 132 equals thickness T5. Invarious embodiments, if after planarizing wear surfaces 232 and 233, athickness of CMC disk 132 is less than thickness T5, additional materialmay be removed from surfaces wear surfaces 232 and 233 so that CMC disk132 can be incorporated into the S5 position of brake assembly 120(i.e., the thickness of CMC disk 132 is reduced to thickness T6).

In various embodiments, CMC disk 134 may be removed from brake assembly120 and incorporated into stator position S5 of brake assembly 220. Invarious embodiments, after removing CMC disk 134 from worn brakeassembly 120, wear surface 234 and/or surface 235 is/are planarized. Invarious embodiments, at least 0.007 inches (i.e., 0.018 cm) may beremoved from one or both surface(s) 234 and 235. In various embodiments,only one surface may be planarized as pressure plate 30 and end plate 32each comprise one wear surface and one non-wear surface. In variousembodiments, between 0.010 inches and 0.02 inches (i.e., 0.025 cm and0.051 cm) of material may be removed from surface 234 and/or fromsurface 235. The amount of material removed from surface 234 and/orsurface 235 is selected such that CMC disk 134 can be incorporated intothe S5 position of brake assembly 120 (i.e., the thickness of CMC disk134 is reduced to thickness T6). The CMC disks may continue to berecycled until they are worn beyond a viable thickness. For example, invarious embodiments, a CMC disk comprising a thickness of less than orequal to 45% of thickness T2 (i.e., 45% of the thickness of a previouslyunused CMC disk) may discarded. In various embodiments, a CMC diskcomprising a thickness of less than or equal to 50% of thickness T2 maydiscarded.

FIGS. 3A and 3B illustrate a method 350 of reusing a friction disk overmultiple brake assembly wear cycles, in accordance with variousembodiments. Method 350 may comprise forming a first brake assembly(step 352). Step 352 may comprise locating a previously unused stator inthe S1 position (step 354), and locating stators of decreasing thicknessin the S2, S3, S4, and S5 positions (step 356). In various embodiments,the stators may comprise a first material (e.g., a CMC material) and therotors of the brake assembly may comprise a second material (e.g., a C/Ccomposite material).

Method 350 may further comprise removing the stators from the firstbrake assembly (step 358) after a wear cycle of the first brakeassembly, removing a portion (i.e., thinning) the stators (step 360),and forming a second brake assembly (step 362). Step 362 may includelocating a previously unused stator in the S1 position of the secondbrake assembly (step 364), and incorporating one or more of the statorsfrom the first brake assembly into the S2, S3, S4 and/or S5 positions ofthe second brake assembly (step 366).

In various embodiments, method 350 may further comprise removing thestators from second brake assembly (step 368) after a wear cycle of thesecond brake assembly, removing a portion (i.e., thinning) the stators(step 370), and forming a new unworn (i.e., third) brake assembly (step372). Step 372 may include locating a previously unused stator in the S1position of the new unworn brake assembly (step 374), and incorporatingstators from a worn brake assembly (e.g., the second brake assembly) inthe S2, S3, S4 and/or S5 positions of the new unworn brake assembly(step 376). In various embodiments, steps 368, 370, and 372 may berepeated as many times as desired.

FIG. 4 illustrates a method 400 of making a brake assembly usingrecycled friction disks. Method 400 may comprise removing a firstfriction disk from a worn brake assembly (step 402). The first frictiondisk may comprise a first material. The worn brake assembly may comprisea second friction disk comprising a second material different from thefirst material. Method 400 may further comprise removing a portion ofthe first friction disk to reduce a thickness of the first friction disk(step 404), and incorporating the first friction disk and a previouslyunused friction disk into an unworn brake assembly (step 406). Invarious embodiments, step 406 may comprise using the first friction diska pressure plate or an end plate of the unworn brake assembly.

In various embodiments, the previously unused friction disk and thethird friction disk may comprise the first material. The thickness ofthe first friction disk may be different from a thickness of thepreviously unused friction disk and from a thickness of the thirdfriction disk. In various embodiments, the first friction disk, thepreviously unused friction disk, and the third friction disk maycomprise non-rotating components of the unworn brake assembly. Invarious embodiments, the first material may comprise a ceramic matrixcomposite material, and the second material may comprise a carbonfiber-reinforced/carbon material composite material.

Benefits, other advantages, and solutions to problems have beendescribed herein with regard to specific embodiments. Furthermore, theconnecting lines shown in the various figures contained herein areintended to represent exemplary functional relationships and/or physicalcouplings between the various elements. It should be noted that manyalternative or additional functional relationships or physicalconnections may be present in a practical system. However, the benefits,advantages, solutions to problems, and any elements that may cause anybenefit, advantage, or solution to occur or become more pronounced arenot to be construed as critical, required, or essential features orelements of the disclosures. The scope of the disclosures is accordinglyto be limited by nothing other than the appended claims, in whichreference to an element in the singular is not intended to mean “one andonly one” unless explicitly so stated, but rather “one or more.”Moreover, where a phrase similar to “at least one of A, B, or C” is usedin the claims, it is intended that the phrase be interpreted to meanthat A alone may be present in an embodiment, B alone may be present inan embodiment, C alone may be present in an embodiment, or that anycombination of the elements A, B and C may be present in a singleembodiment; for example, A and B, A and C, B and C, or A and B and C.Different cross-hatching is used throughout the figures to denotedifferent parts but not necessarily to denote the same or differentmaterials.

Systems, methods and apparatus are provided herein. In the detaileddescription herein, references to “one embodiment”, “an embodiment”, “anexample embodiment”, etc., indicate that the embodiment described mayinclude a particular feature, structure, or characteristic, but everyembodiment may not necessarily include the particular feature,structure, or characteristic. Moreover, such phrases are not necessarilyreferring to the same embodiment. Further, when a particular feature,structure, or characteristic is described in connection with anembodiment, it is submitted that it is within the knowledge of oneskilled in the art to affect such feature, structure, or characteristicin connection with other embodiments whether or not explicitlydescribed. After reading the description, it will be apparent to oneskilled in the relevant art(s) how to implement the disclosure inalternative embodiments.

Furthermore, no element, component, or method step in the presentdisclosure is intended to be dedicated to the public regardless ofwhether the element, component, or method step is explicitly recited inthe claims. No claim element herein is to be construed under theprovisions of 35 U.S.C. 112(f) unless the element is expressly recitedusing the phrase “means for.” As used herein, the terms “comprises”,“comprising”, or any other variation thereof, are intended to cover anon-exclusive inclusion, such that a process, method, article, orapparatus that comprises a list of elements does not include only thoseelements but may include other elements not expressly listed or inherentto such process, method, article, or apparatus.

What is claimed is:
 1. A brake assembly in an unworn state, comprising:a friction disk stack comprising: a plurality of rotors each comprisinga first material, and a plurality of stators interleaved between therotors, the stators comprising a second material different from thefirst material, wherein a wear rate of the first material is differentfrom a wear rate of the second material, and wherein a of a first statorof the plurality of stators is greater than a thickness of a secondstator of the plurality of stators; and a pressure plate located at afirst end of the friction disk stack, the pressure plate comprising thesecond material, wherein a thickness of the pressure plate is less thanthe thickness of the second stator.
 2. The brake assembly of claim 1,further comprising an end plate including the second material andlocated at a second end of the friction disk stack opposite the firstend of the friction disk stack.
 3. The brake assembly of claim 2,wherein a thickness of the end plate is less than the thickness of thesecond stator.
 4. The brake assembly of claim 3, wherein the thicknessof the end plate is less than the thickness of the pressure plate. 5.The brake assembly of claim 1, wherein the first material comprises acarbon fiber-reinforced/carbon matrix composite material.
 6. The brakeassembly of claim 5, wherein the second material comprises a ceramicmatrix composite material.
 7. The brake assembly of claim 1, wherein atleast one stator of the plurality of stators comprises a recycledstator.
 8. The brake assembly of claim 1, wherein a thickness of a thirdstator of the plurality of stators is less than the thickness of thefirst stator and greater than the thickness of the second stator.
 9. Abrake assembly in an unworn state, comprising: a friction disk stackcomprising: a plurality of rotors approximately equal in thickness andeach comprising a first material, and a plurality of stators interleavedbetween the rotors, the stators comprising a second material differentfrom the first material, wherein a wear rate of the first material isdifferent from a wear rate of the second material, and wherein athickness of a first stator of the plurality of stators is greater thana thickness of a second stator of the plurality of stators; and apressure plate located at a first end of the friction disk stack, thepressure plate comprising the second material, wherein a thickness ofthe pressure plate is less than the thickness of the second stator. 10.The brake assembly of claim 9, further comprising an end plate includingthe second material and located at a second end of the friction diskstack opposite the first end of the friction disk stack.
 11. The brakeassembly of claim 10, wherein a thickness of the end plate is less thanthe thickness of the second stator.
 12. The brake assembly of claim 11,wherein the thickness of the end plate is less than the thickness of thepressure plate.
 13. The brake assembly of claim 9, wherein a thicknessof a third stator of the plurality of stators is less than the thicknessof the first stator and greater than the thickness of the second stator,and wherein a first rotor of the plurality of rotors is adjacent to thepressure plate and the first stator.